99 Blue Bird

iTrader: (3)

im fully aware of what those two posts are explaining to do. but i guess what im confused on is all of my valves are closed because i just bolted on new heads. so do i need to put in my stock 7.400 pushrods back in and bolt the rocker arms down. than turn the motor over a couple times and when one of the cylinders valves are open pull the closed valves pushrod and slide the pushrod length checker in and the set it? do you understand what im trying to get at?

ZeeOSix

Yes, pretty much - but you really only need to do the check on one or two valves unless you think there might be a variation between them, which there really shouldn't be. No need to install all the pushrods and rocker arms.

The ultimate goal is to setup the motor so the valve you're checking has the lifter on the base circle of the cam - and that valve will be closed. Then install the adjustable pushrod set to shorter than you need. Then install and tighten the rocker arm to 22 ft-lbs. Then lengthen the adjustable pushrod until you have zero lash. Take note of what the length of the adjustable pushrod is at that point. Then add to that length the amount of lifter per-load you plan on running.

Full Power

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G Atsma

What took ya so long??? LOL

grinder11

iTrader: (1)

Dian

yes, very funny because so much is wrong above:

1. do not torque down the nut when counting turns, finger tight on the socket is just right. (if your finicky use an indicator).
2. one turn on the 1.25mm pitch nut moves the cup by 1.25 x 1.59 (2.7/1.7 for stock ratio) = 1.99mm = 0.078".

for refence: on a stock ls1 preload is 1.50 - 1.75 turns (117 - 137 thou) . plunger travel is about 5.25mm (0.200"). +/- 25 thou on the push rod doesnt matter with stock lifters.

edit: biggest caveat: state of the lifter (pumped up/collapsing/fully collapsed).

stockA4

Lower preload = More lifter travel so slightly better lower RPM power, at the cost of some high RPM stability.

Higher preload = less lifter travel so slightly better higher RPM power at the cost of nothing.

I know which one I would choose each and every single time.

Fast355

Yes and No.

The lifter that has the plunger the highest in the bore will be more tolerant to a valve train that loses stability aka spring float. The deeper the pushrod is in the lifters travel the more the lifter can "pump up" if the valves float or the springs lose stability from harmonics. Longer pushrod will trade-off some low-speed power, idle vacuum and idle quality for increased power and vice versa. I have long gone against the FSM spec of 1 turn from zero lash on hydraulic lifters on the SBC. I have used 1/4 turn on them for hundreds of thousands of miles, it is alot safer when you turn alot of RPM. If the lifters pump up from spring float and the lifter plunger is 0.100" depressed it will add 0.100" to your lift when the valve opens that some engines may not have PTV for. Bent/broken valves and a catastrophically failed engine can be the result. Racing classes that require hydraulic lifters often have guys fit shims inside the lifter between the body and plunger to limit travel as well as they fit them with snap rings in place of the clips. The snap rings in place of the wire clips allow a better margin of safety when running nearly no preload for higher rpm stability.

G Atsma

Not sure it applies here, but back in the bad old days (60's-70's) when I worked at a Shell station where we did a fair amt. of mechanical work, it was common to adjust the SBC lifters a half turn or a bit more down from the clatter threshold. My boss only did about a 1/4 turn or even a bit less to prevent pump-up. Not sure it mattered, but he felt good about it.

stockA4

My statement comes from my experience with Gen 3 LS engines with the oem stock type lifters, Gen 3 LS Is all this forum is supposed to be about, I've broken springs before with the preload on the lower side, never on the high side with these engines. All I did was put longer push rods in it and no more broken springs, I'm racing my cars every weekend (could care less about the slightly worse idle yada yada) I'm spending solid minutes at a time between 5K -7.5k with LS6 springs well you guys are spending a fortune on your valve trains for street engines. Mine's still daily driver too.

however whatever the application may be why not just use camshaft lobes and The proper recommended springs for said lobes that don't float the valves in the RPM range you're going to be planning on setting the preload lower to protect them from floating in!?
I may color out the side the lines a little bit when it comes to my approach to building my cars, cam specs I like etc, but this kind of stuff, If the factory stock engine can handle hundreds of thousands of miles of abuse, why re-engineer the whole thing?

I rather get a Gen 4 engine and mess around with the VVT and keep the stock springs in it then try a bunch of fancy tricks with static valve timing that I know I would end up screwing up.

https://www.motortrend.com/how-to/18...d-performance/

I posted this before. How many people have blown up their engines since reading this article?

Fast355

The rod bearings and lifters were literally the two carry overs from a later SBC in the LS1s. My buddy had a Summit Racing Stage 3 truck cam in his LQ4 build in his 2 door Yukon. When we were street tuning it, with 7.45" pushrods and LS6 springs it floated the valves so badly at 6,200 it felt like fuel cut. He ended up with BTR double springs and it would spin 6,800 no problem. When he pulled the heads, the valves had hit the pistons and several were bent.

stockA4

The lifters yes they are the same but they're also inside an engine with poor oiling designed for a 1.5 rocker with otherwise less than ideal valve train geometry. The LS engine makes better use of those lifters than an SBC does, Just like with its decent rod ratio (4.8L has awesome rod ratio) the same bearing is still adequate.

What year lq4 engine and what lifters did he use? It really sucks when something doesn't work like it's supposed to, especially when so many many many many many others are using the same parts without issue but he had to replace probably a lot more than just the springs to fix it if you say the valves were bent, so What heads? Machine work? Did you set up the valve train in it or watch him do it? Maybe he put his new valve seals on top of the old ones without taking the old ones off. Was he using roller rockers or anything else?

I have a friend at Auto X with a j/y 5.3L swapped fox mustang with the same summit 8713 camshaft. It's got LS6 springs in it and I believe still the stock pushrods. He's way less sympathetic of a driver than I but it's holding up just fine as it's intended to do. I think he set his rev limiter at like 7k and it lives there.


​​​​​It's funny you mentioned this now because I pick on summit all the time however I have personally ran the summit 8714 (same lobes, Just a few more degrees and intake duration) camshaft in both of my cars in my signature The first car it was in there for over a year (went through an entire season of autocross bouncing it off the rev limiter, same 7200 RPM rev limiter same 7.450 pushrods and LS6 springs that had already been through two or three other camshafts at least 60k abusive miles on them already.

MY drag racey car when that camshaft was in it (I had it in this car first there's an old thread about it in the drag race section), It was in there for probably two and a half or three years, Saw 6,800 RPM shift points All day long two seasons of sportsman bracket, same length push rods, same springs, no float no issues at all.

There's three vouchable examples just by my of this setup working just fine as it's intended to with no float or any other issues.

Go on YouTube and every good old boy with a chevy truck or an LS swap has an idle video of their engine with that cam in it with exactly the same setup. What was the stock rev limit of the 5.7L LS6 again?

Fast355

No part in building or setting up the engine. I think it was a LQ4 block with LS2 pistons and rods with unmachined 799 heads and stock rockers with trunion upgrade.

LS6 heads have much lighter sodium filled valves and the stock LS6 cam profile is much less aggressive. These aftermarket grinds can have alot of lifter "toss" at high rpm from the lobe intensity. LS6 cam was GM engineered to run with those springs to its rev limit. Them again even GM gets it wrong sometimes (LS7 dropping valves).

He swapped the springs and ran it for a while not knowing it had bent valves. Later he pulled the heads and that is when he found the valve contact and bent valves. I think it still has the same pistons in it to this day. It did not bend the Comp thick wall pushrods either.

Not saying something was not wrong with the setup, but it was a situation that could have been much worse.

For me unless it is a mild cam with shift points under 6K, I will not use beehives. Even my SBC that makes peak HP at 5,600 rpm with a fuel kill set at 6,000 rpm has dual springs with 375 lb open pressure and milder magnum high lift lobes, even with 100K on the springs it will not have valve control issues. Why skimp $500; when springs, rockers and pushrods are probably the worst abused parts in an engine with an aggressive cam. Failure in the valvetrain can cost the whole engine from pan to cylinder heads.